2. Texts Recommended
โข Engineering Thermodynamics โ
P K Nag
โข Thermodynamics โ J P Holman
โข Thermodynamics โ Yunus A
Cengel
โข Fundamentals of Engineering
Thermodynamics โ
E Rathakrishnan
โข Engineering Thermodynamics โ
3. INTRODUCTION
โข Thermodynamics can be def ined
as t he science of energy
โข Word โThermodynamicsโ
originat es f rom t he greek words
t her me[heat ] and dynamis[power]
โข The early underst anding of
t her modynamics cent ered around
t he concept of get t ing power
f rom hot bodies or f rom heat ,
6. Macroscopic V/S
Microscopic Approach
โข It is well-known that substances
consists of a large number of
particles called molecules
โข The properties of a substance
depend on the behaviour of these
particles
โข For example, the pressure of a gas
in a container is the result of
momentum transfer between the
7. MACROSCOPIC APPROACH
โข Macroscopic approach to the study
of thermodynamics does not
require a knowledge of events
occuring at the molecular level.
โข These effects can be perceived by
human senses or measured by
instruments. Eg:- Pressure,
Temperature etc.
โข This approach is also called
CLASSICAL THERMODYNAMICS
8. MICROSCOPIC APPROACH
๏ In this method, the property
of a system is considered to
be the result of average
behaviour of large groups of
individual particles[molecules]
๏ It is also called STATISTICAL
THERMODYNAMICS
๏ In microscopic approach, the
effect of molecular motion is
9. โข Certain quantity of matter or a region in space
chosen for study is called a system
โข The mass or region outside the system is
called the surroundings
โข The surface which separates the
system from the surroundings are
called the boundary
โขThe boundary of a system can be
fixed or movable
โขItโs the contact surface shared by
SYSTEM ANd SURROUNdINGS
12. OPEN SYSTEM
โข Open systems are those in which we
permit both energy and mass to
cross the system boundary in either
direction (from the system to
surroundings or vice versa)
โข In analysing open systems, we typically
look at a specified region of space, and
observe what happens at the boundaries
of that region.
โข Most of the engineering devices are open
system.
13.
14. CLOSED SYSTEM
๏ผClosed systems are those in which
we permit only energy to cross the
system boundary in either
direction (from the system to
surroundings or vice versa)
๏ผIts also called a control mass
๏ผMass is not allowed to cross the
system boundary
๏ผThe volume need not be fixed in
this case [eg:- a piston cylinder
15.
16. ISOLATED SYSTEM
โข Isolated Systems are those in which
there is no interaction between
system and the surroundings.
โข It is of fixed mass and energy, and
hence there is no mass and energy
transfer across the system
boundary.
17.
18. HOMOGENEOUS AND
HETEROGENEOUS SYSTEM
โข A quantity of matter homogeneous throughout in chemical
composition and physical structure is called a phase
โข If the substance within the system exists in a single phase like
liquid, solid or gas, then the system is called homogeneous
system
โข In these systems, substance should exist only in one phase
โข If the substance within the system exists in more than one
phase, then the system is called heterogeneous
Eg:- water and steam
19. PROPERTY
โข A property of a system is defined as any identifiable
and observable characteristic features by which a
system can be specified
โข Eg : - Pressure, Volume, Temperature etc.
โข These are all macroscopic in nature
20. Intensive and Extensive properties
โข Propert ies which are
independent of t he mass of t he
syst em are called int ensive
propert ies
Eg:- Pressure, Temperature, Densityetc.
โข Propert ies which depends on t he
mass of t he syst em are called
ext ensive propert ies
Eg:-Volume, energyetc.
21. โข Specif ic ext ensive propert ies,
i.e, ext ensive propert ies per unit
mass, are int ensive propert ies.
Eg:- Specific volume,
specific energy etc.
22. โข When all t he propert ies of a
syst em have def init e values, t he
syst em is said t o exist at a
def init e state
โข Propert ies are t he coordinat es
t o describe t he state of a
system
โข Any operat ion in which one or
more of t he propert ies of a
23. โข The succession of st at es passed
t hrough during a change of st at e
is called t he path of t he change
of st at e
โข When t he pat h is complet ely
specif ied, t he change of st at e is
called a process
โข I f af t er a number of processes,
t he syst em comes back t o it s
24. THERMODYNAMIC
PROCESS
โข Any change that a system undergoes from one
equilibrium state to another is called a process
โข The series of states through which a system
passes during a process is called the path of the
process
โข To describe a process completely, one should
specify the initial and final states of the process
and the path it follows
25. โข There are reversible processes and irreversible
processes
โข A reversible process or a quasi-static process is
represented by a solid dark line
โข An irreversible process is denoted by a dashed
line
26.
27. CONTINUUM
โข Mat t er is made up of at oms t hat are widely
spaced in t he gas phase
โข But it is very convenient t o disregard t he
at omic nat ure of a subst ance and view it as
a cont inuous, homogeneous mat t er wit h no
holes, t hat is, a cont inuum
โข From macroscopic point of view we deal
wit h volumes which are very large compared
t o it s molecular dimensions.
โข Wit hin t his volume span, we can assume t he
subst ance t o be cont inuous
โข Thus, t he concept of cont inuum goes hand
28.
29. QUASI STATIC PROCESS
โข The word โQuasiโ means โalmostโ
โข โQuasi-staticโ process is an almost
static or stationary process
โข Infinite slowness is the characteristic
feature of a quasi-static process
โข So a quasi static process is also a
reversible process
โข Infinite time is required to execute a
quasi static process
32. THERMODYNAMIC EQUILIBRIUM
โข A system is said to exist in a state
of thermodynamic equilibrium
when no change in any macroscopic
property is registered, if the system
is isolated from its surroundings
โข An isolated system always reaches
in course of time a state of
thermodynamic equilibrium and can
never depart from it spontaneously
โข A system is said to be in
thermodynamic equilibrium if its in
33. โข Mechanical equilibrium
โข A syst em is said t o be in mechanical
equilibrium when t here is no
unbalanced f orce act ing on any part of
t he syst em or t he syst em as a whole
โข Thermal equilibrium
โข A syst em is said t o be in t hermal
equilibrium when t here is no
t emperat ure dif f erence bet ween t he
part s of t he syst em or bet ween t he
syst em and it s surroundings
โข Chemical equilibrium
โข A syst em is said t o be in chemical
equilibrium when t here is no chemical
34. PATH AND POINT FUNCTIONS
โข Path isthelocusof all pointsthrough
which thesystem passesin itschange
from onestateto another
โข It ispossibleto go from state1 to state
2 along different pathsasshown in the
figure[i.e, thorough A, B or C]
โข Propertieslikepressure, temperature,
volumeetc. doesnot depend on the
path followed in reaching thestate, but
35. โข Characteristics of a process which depends upon the
path followed in going from one state to another are
referred to as path functions
โข Eg:- Work transfer, heat transfer etc.
โข Path functions are not properties of system, while point
functions are properties of system
